In the preface to his text, Molecular Photochemistry, published in 1967 (W. A. Benjamin, Inc.; N.Y.), N. J. Furro noted a "tremendous surge of interest and activity in photochemistry" which had occurred in the preceding decade. The number of since-issued patents on photochemical processes testifies to a continued growth in activity (and interest). For example (and as evidence of the wide applicability of photochemistry), the following specific patents may be noted.
U.S. Pat. No. 3,775,275 Preparation of oxiranes from paraffins. PA1 U.S. Pat. No. 3,937,956 Isotope separations. PA1 U.S. Pat. No. 3,736,240 Chlorination of vinyl chloride polymer. PA1 U.S. Pat. No. 4,012,301 Hydrocarbons from CO and H.sub.2. PA1 U.S. Pat. No. 4,182,663 Conversion of O.sub.2 to O.sub.3. PA1 U.S. Pat. No. 4,026,778 Isomerization of Vitamin A compounds. PA1 U.S. Pat. No. 3,945,897 Preparation of halolactams. PA1 U.S. Pat. No. 4,004,996 Fluorination of amines, amino acids, polyamides, etc., with liquid HF/F.sub.2. PA1 U.S. Pat. No. 3,902,980 CH.sub.3 --CHCl.sub.2 +Cl.sub.2 +O.sub.2 .fwdarw.CH.sub.3 COCl. PA1 U.S. Pat. No. 4,144,152 Kepone degradation with aq. base or H.sub.2. PA1 U.S. Pat. No. 3,554,887 Photochlorinations in radiation-transparent plastic capillaries. PA1 U.S. Pat. No. 4,000,050 Oxidation and skeletal rearrangements of "Santalene" hydrocarbons. PA1 U.S. Pat. No. 3,923,620 Trialkyl or trialkenyl phosphites to phosphates. PA1 U.S. Pat. No. 3,963,570 Addition of (BuO).sub.2 P-OH to C.dbd.C in an oleamide. PA1 U.S. Pat. No. 4,104,145 Benzene+NO.sub.2 +O.sub.2 .fwdarw.nitrobenzene. PA1 U.S. Pat. No. 4,105,520 Cyclohexane+NO.sub.2 +O.sub.2 .fwdarw.adipic acid. PA1 U.S. Pat. No. 4,045,316 Removal of vinyl chloride from gas streams. PA1 Brit. Pat. No. 1,462,722 SO.sub.2 & NO.sub.2 removal from effluent gases. PA1 Jap. Pat. No. J5 2033-882 Removal of NH.sub.3 from effluent gases. PA1 Jap. Pat. No. J5 5011-055 Removal of mercaptans and sulfides from effluent gases.
Of particular interest with regard to the present invention is U.S. Pat. No. 3,926,556, which is directed to the destruction of pyrogens in biological and organic fluids by the synergistic action of ultraviolet and microwave irradiation on macromolecular components of the pyrogens. The above listed U.S. Pat. No. 3,554,887 is also of high interest, as disclosing U.V.-transparent capillaries consisting of polymers of ethylene or chloro/fluoro-substituted C.sub.2 /C.sub.3 olefins.
The foregoing '556 patent discloses the use of a plurality of capillary tubes (disposed around or parallel to a U.V. lamp) through which the fluid to be treated is passed. In this manner, the maximum thickness of the body of the fluid being irradiated is no greater than the inner diameter of the tubes, which may be as small as 0.1 mm. Thus, even when the fluid is one--such as blood--which strongly absorbs U.V., a major proportion of the fluid is penetrated by the radiation. Various apparatus arrangements by means of which the fluid passing through the tubes is simultaneously subjected to the action of microwaves are also disclosed in the patent.
It is evident that the thickness of the fluid body being treated could be reduced even further by using smaller diameter capillaries. Glass capillaries of hair-like dimensions are known. U.S. Pat. No. 3,268,313 discloses a method of melt-spinning "hollow fibers" (from ordinary glass) having outer diameters of from 7.5 to 75 microns (and having from 10 to 65% of their volume hollow). No reason is apparent why comparably sized hollow fibers could not be made from U.V.-transparent glasses, such as silica or VYCOR (registered trade name of Corning Glass Co., Inc.), at least by flame-drawing. Methods of forming headers or "tubesheets" in combination with glass fibers are also known (see, for example, U.S. Pat. No. 4,219,613). Presumably, such methods could be adapted to structures of the type shown in the '556 patent (FIGS. 1 and 1A, specifically), i.e.--structures in which the fibers would be disposed in parallel array around a cylindrical U.V. lamp (assuming that the matches of expansion coefficients appropriate to the contemplated operating temperatures could be attained for the fibers, tubesheet, etc.). It is also known that blood can be passed through hairlike hollow fibers (witness the now well-known hollow-fiber type "artificial kidney" or dialyser) without serious difficulty (at least from heparinized patients). Thus, although the prior art itself does not contemplate so doing, it would appear feasible to practice the process of the '556 patent with capillaries having hairlike dimensions, thereby achieving a substantial reduction in the thickness of the fluid "layer" being irradiated (and in the thickness of the capillary wall that the radiation must penetrate). This, of course, is with the proviso that the fibers would have to be positioned around the U.V. lamp in such manner that the innermost fibers would not block off exposure of the outer fibers to the radiation (a reflector around the outside of the fiber array not being feasible for the '556 process because it would interfere with microwave coupling with the materials inside).
If it were possible somehow to irradiate each fiber from all sides, a relatively large number of fibers could be used without concern for mutual shading and the thickness of the fluid the radiation would have to pass through in order to achieve complete penetration would be only half the inner fiber diameter.